The BX 16V like the Mi16 have those "Recaro type" seats with the creases pulled down along the base & back. I have worked it out that prior to me buying the car, some low life obviously flogged it & during the joy ride managed to mount a kerb & give me 4 square wheels; hopefully he was seriously or preferrably fatally injured, that way he won't stuff up anybody elses pride & joy, however, this incident made the previous owner paranoid about car security & I would say they have fitted one of those *ultimate car protection* type steering locks for $8.95 from Supercheap or somewhere similar.
When they have fitted it to the wheel, they have then jammed the base down on to the drivers seat. Now; the pleats/creases in these seats are formed by a piece of wire which is sewn into the backing of the upholstery & then pulled down towards the lower seat base to hold it into position. If you ever think of using one of these useless devices or even a dearer one ($9.95 ) then be very careful that you don't do as these folks did & bend this wire. The wire is held in position by a small piece of chain which is slipped over each end of the wire. Naturally once it gets bent, the chain simply falls off. This ceates two problems; the seat appears to have almost collapsed, & if you're not very careful, one end or both of the wire will simply poke through your upholstery & make the seat & in fact the car look VERY second hand. Not only that, but it could give you or some other unsuspecting driver an unexpected thrill
Prevention: If you must use that type of "protection" keep the bottom part well clear of this area of the seat.
To rectify: Adjust seat fully back & look under. There you will see two wire clips attached from the seat base to a round cross bar which has upholstery wrapped around it to prevent rattles. Prise these off either using fingers or carefully with a screw driver. Lift the front edge of the seat from the frame, whereupon you will find two rubber straps connected from the back of the seat to a couple of hooks under the seat base. Disconnect. Carefully using a medium sized screwdriver, unclip the upholstery from the front & rear of the seat base (one end has 3 clips whilst the other is a full length strip. You will find two circular white/clear plastic discs attached to the bottom of each crease, about the size of a 20cent piece. Attached to them will be the chain which is used to hold the wire. Remove the chain but leave the discs in place. Go to the local hardware store & buy about 300 mm (one foot) of bathplug chain (using a piece of the old chain as a check on hole size) Cut the bath plug chain into two pieces. Get a piece of insulated semi pliable copper wire (same as electricians use for house wiring) about a foot long & bare the last inch or so & connect to the top of a piece of chain. Check to be sure that the wire inside the seat is fairly straight, if not, straighten same before you start. Slide end of copper wire through the hole & proceed to pull the chain through until the end with the hole in it is around level with the end of the wire; connect to wire (Note: as the copper wire comes out on the seat bottom, be sure to guide it through between the spokes on the plastic disc). Disconnect the chain from the copper wire & feed the chain through the 4 way split hole in the centre of the plastic disc. It is important to remember (if you didn't heed the advice I gave earlier about leaving the disc in position) that the centre of the disc must be pointing upwards/towards you when the chain is fed through. Just put enough tension on the chain to hold into position & repeat the fitting procedure to the other end of the wire. Check that an even distance protrudes from both sides of the wire past the pocket in which it sits, and then pull each side through with a pair of pointed nosed pliers. When in position, cut off chain one link up from the plastic disc with a pair of sidecutters, & twist the remaining link or fit a tie wire in to prevent slippage.
Clip upholstery back into front & rear mountings on seat, fit black rubber ties to clips under the seat, push wire clips back into position, using a hammer handle or piece of timber bumped with the palm of the hand to make clips seat.
The whole operation should not take more than 15 minutes & the front seat looks & feels like new again. Have fun; I did!!

Alan S